* The updates from the previous press release are underlined.
All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.
Unit 1 (Shut down)
- Explosive sound and white smoke were confirmed after a big quake occurred at 3:36 pm on March 12, 2011. It was assumed to be hydrogen explosion.
- At 3:37 pm on March 25, 2011, we started injecting freshwater to the reactor and are now injecting fresh water by a motor driven pump powered by the off-site transmission line.
- At 10:11 am on December 10, 2011, in addition to water injection from water feeding system, we started water injection from piping of core spray system to the reactor.
The current amount of water injection from the feed water system is approx. 4.8 m3/h and that from the reactor core spray system is approx. 2 m3/h.
- At 1:31 am on April 7, 2011, we commenced injection of nitrogen gas into Primary Containment Vessel.
- At 11:22 am on August 10, 2011, we started cyclic cooling for the water in the spent fuel pool by an alternative cooling equipment of the Fuel Pool Cooling and Filtering System.
- At 4:04 pm on November 30, 2011, we started operation to inject nitrogen into the reactor pressure vessel.
- At 6:00 pm on December 19, 2011, a full-scale operation of the PCV gas management system started.
Unit 2 (Shut down)
- At approximately 6:00 am on March 15, 2011, an abnormal noise began emanating from nearby Pressure Suppression Chamber and the pressure within the chamber decreased.
- At 10:10 am on March 26, 2011, we started injecting freshwater to the reactor and are now injecting fresh water by a motor driven pump powered by the off-site transmission line.
- At 2:59 pm on September 14, 2011, in addition to water injection from feed water system, we started water injection from piping of core spray system to the reactor.
The current water injection amount from the reactor feed water system is approx. 2.7 m3/h and that from the core spray system is approx. 6m3/h.
- At 5:21 pm on May 31, 2011, we started cyclic cooling for the water in the spent fuel pool by an alternative cooling equipment of the Fuel Pool Cooling and Filtering System.
- At 8:06 pm on June 28, 2011, we started injecting nitrogen gas into the Primary Containment Vessel.
- At 6:00 pm on October 28, 2011, a full operation of the PCV gas control system started.
- From 9:40 am to 12:30 pm on March 26, the water level and water temperature inside the PCV of Unit 2 was investigated with the industrial endoscope. As a result, the water level was confirmed to be 60 cm from the bottom of the PCV and the water temperature was confirmed to be in the range of approx. 48.5 °C to 50.0 °C. From 9:30 am to 10:30 am on March 27, we measured ambient dose rates of inside of PCV by inserting a dose rate meter around the upper part of grating through one of the penetration points of PCV (X-53 Pene). We confirmed that an ambient dose rate was 31.1 to 48.0 Sv/h at the point of approx. 50 cm inside from the edge of the penetration point (PCV side) towards the center. Another was 39.0 to 72.9 Sv/h at the point of approx. 1m inside from the edge towards the center.
- At 10:46 am on December 1, 2011, we started the nitrogen injection to the Reactor Pressure Vessel.
- At 11:50 am on January 19, 2012, we started the operation of the spent fuel pool desalting facility.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01 am on March 14, 2011. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, 2011, we started injecting fresh water to the reactor and are now injecting fresh water by a motor driven pump powered by the off-site transmission line.
- At 2:58 pm on September 1, 2011, we started water injection by core spray system in addition to water injection by the reactor feed water system piping arrangement.
The current water injection amount from the reactor feed water system is approx 1.8m3/h and that from the core spray system is approx. 4.9m3/h.
- At 7:47 pm on June 30, 2011, we started cyclic cooling for the water in the spent fuel pool by an alternative cooling equipment of the Fuel Pool Cooling and Filtering System.
- At 8:01 pm on July 14, 2011, injection of nitrogen gas into the Primary Containment Vessel started.
- At 4:26 pm on November 30, 2011, we started operation to inject nitrogen into the reactor pressure vessel.
- At 7:00 pm on March 14, 2012, the regular operation of the PCV gas control system started.
Unit 4 (Outage due to regular inspection)
- At around 6 am on March 15, 2011, we confirmed an explosive sound and the sustained damage around the 5th floor rooftop area of Reactor Building.
- At 12:44 pm on July 31, 2011, we started cyclic cooling for the water in the spent fuel pool by an alternative cooling equipment of the Fuel Pool Cooling and Filtering System.
- From 2:00 pm to 4:40 pm on March 27, Hydrazine injection into the Unit 4 reactor well through the instrument pipes inside the reactor was conducted.
- At 10:58 am on November 29, 2011, in order to decrease more salinity, we installed Ion exchange equipment and started the operation of such equipment.
- At 5:41 am on March 27, the cooling of the spent fuel pool of Unit 4 was stopped (water temperature at the time of stoppage: approx. 24 °C) in order to implement the replacement of flexible hose in the primary coolant system and pump inlet strainer in the secondary coolant system. Stoppage is scheduled to continue till March 28. The increasing rate of the water temperature is estimated to be approx. 0.5 °C/h, therefore no material issue in the management of the pool temperature is expected.
- At this moment, we don't think there is any reactor coolant leakage inside the primary containment vessel.
Unit 5 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 5:00 am on March 19, 2011, we started the Residual Heat Removal System Pump in order to cool the spent fuel pool.
- At 2:45 pm on July 15, 2011, we started the operation of the original Residual Heat Removal System (System B) by its original seawater pump.
- At 10:11 am on December 22, 2011, since we finished the recovery work of seawater pump (System B) of equipment water cooling system, we made a trial run. At 11:25 am on the same day, we confirmed no abnormalities and restarted the operation.
- At 7:05 am on March 28, 2012, we stopped Shutdown Cooling System due to suspension of power supply for construction work regarding power supply cars installation in case of outage of AC power source of Unit 5 and 6. Due to this work, cooling the reactor stopped (water temperature of the reactor when sftopped: approx. 32.3°C). At 2:56 pm on the same day, we restarted Shutdown Cooling System and re-started cooling the reactor. (water temperature of the reactor when restarted: approx. 38.2°C)
Unit 6 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 10:14 pm on March 19, 2011, we started the Residual Heat Removal System Pump of Unit 6 to cool down Spent Fuel Pool.
- At 2:33 pm on September 15, 2011, we started separately cooling the reactor through the Residual Heat Removal System and the spent fuel pool through Equipment Cooling Water System and Fuel Pool Cooling System.
Others
- At around 10:00 am on June 13, 2011, we started the operation of the circulating seawater purification facility installed at the screen area of Unit 2 and 3.
- At 8:00 pm on June 17, 2011, we started operation of Water Treatment Facility against the accumulated water. At 6:00 pm on July 2, we started the circulating injection cooling to inject the water, which was treated by the accumulated water treatment system, to the reactors through the buffer tank.
- At 7:41 pm on August 19, 2011, we started treatment of accumulated water by parallel operation of one line from the cesium adsorption instrument to the decontamination instrument and the other treatment line of the cesium adsorption instrument No.2.
- At 2:06 pm on October 7, 2011, we started to spray purified accumulated water brought from Unit 5 and 6 continually in order to prevent dust scattering and potential fire outbreaks from the cut down trees.
- On October 28, 2011, we started installation of the water proof wall at the sea side, in front of the existing shore protection, Units 1-4, in order to contain marine pollution by underground water.
- At 12:25 pm on December 13, 2011, we started the re-circulating operation of desalination facility (reverse osmosis membrane) for the purpose of suppression of condensed water after desalination treatment.
- At around 8:30 on March 26, 2012, in the area of condensed water tanks for water desalinations (reverse osmosis membrane) of Fukushima Daiichi Nuclear Power Station, a partner company worker found that water was leaked from a pipeline (anti-pressure hose) which transferred the condensed water from the water desalinations to the condensed water tanks. In order to stop the water leakage, we stopped the transfer pumps of the water desalinations (reverse osmosis membrane) and then the leakage stopped. After that, we closed the valves at the both sides to the leakage point of the pipeline (anti-pressure hose). When we checked the leakage on the site later, we found that a part of the leaked water had been poured into a nearby drainage for general draining water. And then, we conducted sampling surveys on the leaked water, the water which was poured into the drainage, and the seawater around the exit of the drainage. As a result, we judged that some water including radioactive materials was poured into the sea from the exit of the drainage located at about 300 m south from the discharge channel of Unit 1-4 of Fukushima Daiichi Nuclear Power Station. At this moment, the water desalinations (reverse osmosis membrane and evaporative concentration apparatus) are not in service. However, because we have much treated fresh water, it does not affect water injection to the reactors. Total amount of leaked water is estimated to be approx 120 m3 in accordance with the operation hour of the pump. Approx. 80 L out of 120 m3 is estimated to flow into the sea at maximum. Thereafter, the cesium adsorption apparatus was stopped at 5:00 pm and the second cesium adsorption apparatus was stopped at 5:29 pm.
At 9:10 am on March 28, 2012, we restarted the 2nd Cesium Adsorption Apparatus after having completed the work against the leakage and it reached to the rated flow (approx 40 m3/h) at 9:20 am on the same day. At the 12:07 pm and 12:13 pm on the same day, we restarted the two lines of the desalination facility (reverse osmosis membrane). As for the Cesium Adsorption Apparatus, power retrofitting work had been conducted in order to establish 2 lines of power sources for accumulated water treatment facility. Thus, after having completed the work, at 2:32 pm on the same day, we restarted the Cesium Adsorption Apparatus and it reached the rated flow (approx. 19.1 m3/h).
- From 10:00 am to 4:00 pm on March 27, we transferred accumulated water from the basement of Unit 6 T/B to the temporary tank. At 10:00 am on March 28, we restarted the transfer.
